[svnt]

> gets us to about 150 trillion humans in 1,000 years

I realize the big issue is settled here but just to scope this detail: the total land area of earth is coincidentally approximately 150 million km^2

At 150 trillion humans each human would get just about a square meter. Many of those square meters are uninhabitable.

[midasuni]

That’s about the density of Kowloon walled city. And ignores the available space in the ocean.

[woobar]

Did they grow any food, produce electricity, or had any manufacturing at all in Kowloon?

[throwaway2037]

To be clear, "Kowloon" is different from "Kowloon Walled City". And, yes, they did have very small manufacturing inside.

I highly recommend that you find a copy of this (in)famous book about it: << City of Darkness>> (https://cityofdarkness.co.uk).